Re: [RFC PATCH v3 3/5] hw/vfio/ap: store object indicating AP config changed in a queue

[Anthony Krowiak <akrowiak@linux.ibm.com>]

On 3/10/25 11:35 AM, Rorie Reyes wrote:
> Creates an object indicating that an AP configuration change event
> has been received and stores it in a queue. These objects will later
> be used to store event information for an AP configuration change
> when the CHSC instruction is intercepted.
>
> Signed-off-by: Rorie Reyes <rreyes@linux.ibm.com>
> ---
>   hw/vfio/ap.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
>
> diff --git a/hw/vfio/ap.c b/hw/vfio/ap.c
> index 3614657218..ddab764ab4 100644
> --- a/hw/vfio/ap.c
> +++ b/hw/vfio/ap.c
> @@ -41,6 +41,13 @@ struct VFIOAPDevice {
>       EventNotifier cfg_notifier;
>   };
>   
> +typedef struct APConfigChgEvent {
> +    QTAILQ_ENTRY(APConfigChgEvent) next;
> +} APConfigChgEvent;
> +
> +QTAILQ_HEAD(, APConfigChgEvent) cfg_chg_events =
> +    QTAILQ_HEAD_INITIALIZER(cfg_chg_events);
> +
>   OBJECT_DECLARE_SIMPLE_TYPE(VFIOAPDevice, VFIO_AP_DEVICE)
>   
>   static void vfio_ap_compute_needs_reset(VFIODevice *vdev)
> @@ -75,11 +82,14 @@ static void vfio_ap_req_notifier_handler(void *opaque)
>   static void vfio_ap_cfg_chg_notifier_handler(void *opaque)
>   {
>       VFIOAPDevice *vapdev = opaque;
> +    APConfigChgEvent *cfg_chg_event = g_new0(APConfigChgEvent, 1);

It doesn't make sense to allocate this before the check below. If the
event_notifier_test_and_clear() fails, you'll have allocated this for no
reason. Allocate cfg_cgh_event prior to inserting it into the queue
below.

>   
>       if (!event_notifier_test_and_clear(&vapdev->cfg_notifier)) {
>           return;
>       }
>   
> +    QTAILQ_INSERT_TAIL(&cfg_chg_events, cfg_chg_event, next);
> +
>       css_generate_css_crws(0);
>   
>   }